The project examines critical transition points in adolescent educational careers, especially the transition from intermediate to high schools, and their relation to drug use. It also measures drug use in Puerto Rican school population at points during two consecutive years and analyzes the characteristics of uses and non-uses in the population. The instruments used are a self-administered questionnaire for students in private and public schools and a questionaire administered to school directors to detect the relation of institutional variables to drug use. The pilot study and resulting revisions are completed, and the first year data are collected and being analyzed in terms of demographic, family, personal, and institutional variables. Data will be collected during the second year from the same sample of students, who will now have passed the transition point, and compared with the first year data.